The present invention relates to a device for guiding an element, such as a spark igniter or a starting injector, extending in an orifice in a wall of a turbomachine combustion chamber.
An annular turbomachine combustion chamber is delimited by coaxial axisymmetric walls which extend one inside the other and which are connected at their upstream ends by an annular chamber endwall comprising air supply orifices and fuel feed means.
The external wall of the chamber comprises, in the vicinity of its upstream end, at least one passage orifice for a spark igniter intended to initiate the combustion of the fuel/air mixture in the chamber. In certain cases, starting injectors, independent of the aforementioned fuel feed means, are likewise mounted in orifices in the external wall and distributed about the axis of the chamber, in order to improve initiation of the combustion of the air/fuel mixture in the chamber, one of these injectors being situated in the vicinity of the or of each spark igniter.
During operation of the turbomachine, the internal and external walls of the combustion chamber expand thermally and are subjected to considerable vibrations, which leads to relative displacements between the external wall of the chamber and the elements (igniters and starting injectors) which are mounted in orifices in this wall and which are supported by an external casing of the combustion chamber.
To compensate for these relative displacements, use is made of devices for guiding these elements which each comprise a ring and a bush which are substantially coaxial and mounted one inside the other, the ring being intended to be traversed axially by the element and comprising an external annular rim guided transversely in an internal annular channel of the bush which is intended to be fastened to the edge of the orifice in the external wall of the chamber.
The ring and the bush delimit around the element a cylindrical annular passage opening into the chamber and inside which can penetrate small quantities of air/fuel mixture which, after a certain time, result in the formation of coke between the device and the element and may therefore interfere with the guidance of the element by the device. Furthermore, the formation of coke may promote the creation of hot points that can weaken the device and the element. Finally, the deposition of coke on a spark igniter may disturb the ignition of the air/fuel mixture.